We proposed and demonstrated a distributed fiber-optic overheating detection sensor using optical time domain refrectometry. With increased of temperature the optical fiber is bended by a bi-metal and it result in optical leaky loss of the fiber. The sensor structure is designed in such a way that the signal of overheating is happen when the temperature exceeding a threshold temperature and the optical fiber is protected from excess bending.Keywords : Fiber-optic sensors, Overheating detection sensor, Optical time domain refrectometry, Bi-metal, Bending loss + Corresponding author : ktkim@honam.ac.kr (Received : Jul. 08, 2013, Accepted : Jul. 23, 2013 This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License(http://creativecommons.org/licenses/bync/3.0)which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.